"Back on Face" Problems

[Eldon Goddard]

Lets see.... I thought I could fix the problem with a new hinge pin as I am a terrible welder and I do not have a welder in the first place. So I put in a new pin from brownells, but I failed to fix the problem in doing so. Then my friend told me he could weld the barrels for me I decided to try that instead. I probably should not have replaced the hinge pin in the first place, but if I had a dollar for every stupid thing I have done I would probably own an Invincible grade not a VHE.

[Bruce Day]

You probably found that the barrel hook does not directly engage a hinge pin; it engages a guide roll through which the hinge pin extends. This is shown in the diagrams in TPS and in Parker catalogs. Replacing the hinge pin does not fix looseness because it is not the bearing surface.

When Parker repaired loose guns, they had jigs that held the frame and prevented it from being bent while the hinge pin was pressed out. The guide roll was removed and a new one inserted in the frame channel, then the hinge pin re-inserted through the roll. Because so many hinge pins are extremely difficult to remove today, the preferred practice today is to weld new material on the barrel hook, then round file to shape, which takes skill and a fine hand.

As an expedient today, some will glue a shim into the barrel hook. This can last for years and costs almost nothing. My personal view is that this is not the best fix but something temporary. I realize that temporary goes on for years for some owners. I should further add that i have never personally done this work, but this is my understanding based upon reading and talking to gunsmiths who do this work as a matter of course. I have had one gun loose on face and fixed by the hook welding method, but I think by the time a gun gets loose on face due to guide roll/hook wear, there are many other wear issues with the gun.

[Cold Spring]

Several friends asked for more info on my technique. Here's a photo collage showing work on a 16 gauge Fox. Same technique would apply to an Ithaca Flues, subject of this thread, except that the end mill would be sized same as the Flues hinge pin.

Just as an aside, I'll add that I started doing this work on my own guns because of sloppy workmanship, multiple times, by gunsmith XYZ who does rejointing work. I worked part time as a machinist while in high school and college, and nowadays have access to a large machine shop owned by two friends. Sorry, I won't badmouth this gunsmith on the world wide web. Please don't ask for his name. Maybe he does better work for others? Last comment, there's no reason why most any gunsmith who owns a vertical mill can't do similar high precision work.

After TIG welding


Milling machine adjusted for +.005" on the X (long axis). In this case it was .0035" for "off face" measurement + .0015" for final fitting


New radius milled in the hook using an end mill sized for a 16 gauge Fox hinge pin


New radius is cut and is ready for fitting. Note how little "heat" propagated to the barrel hook


Fitting about 1/2 way complete using oil lamp soot


I like to use Dykem (machinist layout blue) for final fitting. Dykem is much thinner than soot. Almost done here but I'll add that most factory done work will show even less contact than in this pic..

[Double Play]

Frank,
Thanks for sharing your procedures in pictures. I’ve made a couple of new roll joints/guide rolls for both hammer and hammerless guns and by adding the needed material was able to achieved the same result with no file fitting. I would be very interested in getting more details on the fixture you used to hold the barrels while machining in case I decide to try the welded hook method. Thanks, Larry

[Twice Shooter]

Yes, please show the fixture. Thanks, Tom

[Eldon Goddard]

I did not have that much contact on the hook but I did have a good amount in the center of the hook. Are not most hinge pins tapered? How do you account for that when milling as end mills are not tapered? I agree that using a vertical end mill would be the best choice and I do have some experience machining. I have access to a vertical mill and even a cnc mill but since it is at my school bringing in a set of barrels is out of the question. I may be able to get the permission, but I doubt it.

[Cold Spring]

Ithaca and Fox hinge pins are straight, not tapered. When working on a gun with a tapered pin, you mill to the small diameter, then match the taper using files and scrapers. Much more complicated and time consuming. For those who asked for a pic of the fixture, here's the best I can do. Fixture is in my cabinet at the machine shop 30 miles from here. I don't have a print. I made it up some years ago while fooling on the mill. First pic shows the complete setup on the mill, with fixture clamped in the table vice, and barrel in the fixture. Also shows the outrigger I use to support the mid part of barrel during the machining. Again, you need "witness" coordinates for the barrel hook radius before doing any welding, so you can revert to the EXACT coordinates after barrel is welded and replaced in the fixture. Then you make table adjustments on the X and sometimes the Y axis for the actual off the face on that particular gun.

Second pic shows the original condition on this gun. .004" thick steel feeler gauge is a tight fit = .0035" off the face IME.

Last pic is for those who do their own soot fitting. Be sure to use a good dust mask to keep the airborne carbon out of your lungs.

[Autumn Daze]

Frank, Great pictures and tutorial. Thanks! I remember when those Kurt Anglelok vises first came out. Thay added so much versatility to the Bridgeport mill verses the old Bridgeport vise. Another nice feature of the Kurt vise is that for every pound of force along the axis of the screw the vise exerts a half pound of force down. Just sayin....

[Eldon Goddard]

Frank,
Thanks for all the help I have decided to use dycem blue as the soot method is just to dirty. Got black on everything from the garage door to my work bench and everything else. The old hinge pin I took out was tapered I checked it with my calipers, however I do not know if it is the original but I would assume it is as the finish on the gun I am pretty sure is original.

[Cold Spring]

Eldon, I am happy to help. Ya know, I should have qualified my earlier statement about Ithaca and Fox hinge pins. I know for a fact that A H Fox and Ithaca NID hinge pins are dead straight because I've rejointed a few of each. HOWEVER, I've never done the earlier Ithaca Flues model and for all I know its hinge pin is tapered. Any Syracuse Arms enthusists out there? SAC used tapered hinge pins and are a challenge to get back on the face because of that design. I did one SAC gun and all I have to say is, never again. Possibly the best way to do that is press out the old pin, fixture the barrels so they are dead on the face + a little bit for wearing in, then line-bore/ream on the mill for an oversize straight or tapered pin. Of course the new pin will have to be dressed off on the sides of the frame which would be very difficult without marring the frame colors on both sides. Just thinking out loud..... Good luck with your project.